Compressor modulating system



United States Patent 3,224,652 (ZQMPRESSQR MUDULATHNG SYSTEM Oscar Oidberg, 7525 l'razer St, Springfield, Va. Filed Feb. 16, 1965, Ser. No. 433,235 5 Claims. (Cl. Bil-22) (Granted under Title 35, US. Code (1952), see. 266) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment to me of any royalties thereon.

The present invention relates to a compressor modulating system and, more particularly, to a compressor modulating system in which the output of a compressor is modulated for progressively controlling the output thereof as a function of demand.

Modulation of compressor output is desirable in refrigeration and air conditioning systems as a means of controlling cooling capacity. Various valving methods and means have heretofore been set forth to accomplish modulation with constant speed compressors. These systems have been proved to be complicated or ineffective. An important feature of a successful system should be the provision of progressive modulation during compression by a means which eliminates unnecessary work of high compression during moderate or low demand conditions. The power saving created thereby is realized throughout by improvement in the overall operation.

The more common method of controlling temperature in air conditioning systems is to cycle the compressor on and off in accordance to the cooling requirement demands. This produces power line surges that can be harmful to other equipment utilizing the same power source. Prior continuous compressor operating systems were provided with a full bypass system to cut 01f the cooling effect in accordance to demand. This provided no relief for full compression and attendant high power consumption when the demand was minimal, since the pressure within the compressor remained at a high level.

The present invention provides a modulating system with a rotary vane type compressor having progressive unloading ports which are successively controlled by a valve which is sensitive to suction pressure fed back from the intake side of the compressor. This bypassing of refrigerant gas during compression reduces power consumption during periods of light or intermediate demand and is accomplished within segments of the cylinder chamher during the compression cycle. The compressor is basically operated at a constant speed and can be produced at a relatively low cost. Since this system operates on compressor pumping output demand, the conventional complicated and expensive bypass means and controls can be eliminated. Also, the efiiciency is kept more nearly constant during all loading conditions. Further, the pressure between the separate chamber-s created by the compressor vanes are intermixed a minimum amount to keep pressure pulses from surging through the several chambers and losing the progressive compression required for efficient operation.

It is, therefore, a feature of this invention to provide a new and improved compressor control system.

It is another feature of this invention to provide a new and improved compressor control system making use of a progressively actuated valve connected to a rotary compressor which modulates the output of the compressor in accordance with circulating output demands.

Still another feature of this invention is to provide a refrigeration or air conditioning system in which the overall con-trol is maintained by system suction pressure means.

Yet another feature of this invention is to provide a compressor control system making use of a progressively actuated valve connected to ports in the compressing area of a rotary compressor which modulates to eliminate compression areas not required, in accordance with system capacity demands.

A further feature of this invention is to provide a constant speed compressor system which operates with a substantial power saving in overall operation.

A still further feature of this invention is to provide a compressor in which unnecessary work of compression is eliminated during moderate or low demand condition.

An additional feature of this invention is to provide a modulating control system which may be built into a constant speed compressor.

Another feature of this invention is to provide a modulating control system for a constant speed compressor in an air conditioning or refrigeration system which enables a simplified structure that can be produced at low cost.

Still another feature of this invention is to provide a modulating control system in which progressive compression is maintained during the compression stroke.

The exact nature of this invention as well as other objects and advantages thereof will be readily apparent from consideration of the following specification relating to the annexed drawing in which:

The figure shows a sectional view of the compressor and modulating valve of this invention combined with block representation of the remainder of the refrigeration system.

Briefly, the compressor modulating system of this in vention makes use of a rotary sliding vane compressor unit which is provided with bypass vents in addition to the normal output passage. These bypass vents, the number of which depends upon the levels of modulation desired, are progressively selected so as to bypass selected portions of the compressed refrigerant at selected specific pressure locations in the compression chambers. That is, Without the bypass vents, the maximum compression pressure is vented through the output passage. When the pressure in the overall system as sensed at the inlet to the compressor reaches a predetermined level, a spool valve is used to open the bypass vents in response to such pressure levels, and the selection of the bypass vents is to progressively reduce the volume of gas being circulated through the system. With this volume being modulated in response to the inlet pressure, the apparatus of this invention provides a means of capacity control which is efficient but does not require extensive nor complicated auxiliary structure. A flow valve is provided to prevent back pressures in the output passage from loading the bypass vents.

In a typical embodiment of this invention, such as is shown in the figure, the rotary sliding vane compressor unit iii is constructed in a conventional manner. Any desired number of sliding vanes 11, such as the six illustrated, as determined by engineering considerations may be used. Vanes 11 are provided to seal the compression chambers which are further bounded by the moving rotor 14, which is mounted on axis 15, and the cylinder walls 16 together with the ends of the cylinder one of which has been removed in the figure. The refrigerant enters the compressor lid through inlet opening 17 and is carried clockwise, as illustrated, around the cylinder 16 in a chamber 13. In the unmodulated condition the refrigerant will leave the compressor through an exit passage 18 situated at the downstream end of the compression chamber. Between inlet opening 17 and exit 18 are located bypass vents, such as vents 19 and 21. The selection of the number of such vents depends upon the pressure levels and the accompanying temperature levels required in specific applications. It is by selective spacing of the vents at points, determined by engineering considerations,

around the circumference of the cylinder 16 that desired percentages of bypass of the refrigerant are provided.

Spool valve 22 is positioned as close as practicable to the cylinder wall 16 in the vicinity of vents 19 and 21. The volume of the fiuid containing vents is limited to a small maximum so as to prevent compression and reexpansion pulses and so as to limit the variations in volume of chambers 13 which would otherwise result from the passing of the vanes 11 by the vents 19 and 21. If the volume of the vent channels exceeds this maximum, variations of pressure within the compressor produce erratic results and loss in efliciency when operating at full capacity with vents closed by the spool valve. Spool valve 22 is made up of a cylinder wall enclosure 23 and a spool-type piston 24 snugly fitting within cylinder 23. The spool piston 24 is made up of a cylinder connector means 25 with enlarged portions 26, 27 and 29 concentrically mounted on connector means 25. These enlarged portions 26, 27 and 29 provide a snug fit within cylinders 23 and provide the proper positioning of the piston. A bleeder channel 31 is connected through the cylinder wall 23 of spool valve 22 at one end, and the other end is connected to the compressor at the inlet opening 17 to sense the suction pressure at such place where the refrigerant enters the compressor. This suction pressure is introduced into the spool valve chamber which surrounds connecting means 25 and is vented through passages 30 to all of the open chambers of the spool valve including top chamber 32. Valve connector means 25 is mounted on a compression spring 28 which is covered by a bellows-type membrane 33 of any suitable flexible airtight material, such as rubber, plastic sheeting, or the like. An adjustable bolt 34 is the means whereby the opposite end of spring 28 is mounted within the bellows chamber of spool valve 22. The bellows is provided with a vent means 35 that enables the bellows 33 to operate with atmospheric pressure on the inside thereof. The positioning of the spool 24 is determined by the balance of forces provided by the suction through vent 31 tending to move the spool toward the adjustable bolt 34 and the tension of spring 28 selected by adjustable bolt 34. Spring 28 is biased to move the spool 24 away from adjustable bolt 34.

When the compressor is in its inoperative condition and all of the pressures throughout the system are substantially equal, the position of spool 24 of spool valve 22 is at its lowermost position toward the spring 23. That means that the compression of the spring is at its maximum and the enlarged portions 26 and 27 of the spool 24 cover the vents 21 and 19, respectively. Before operation, exit passage 18 is the only open exit opening.

When the rotor 14 is operated, the pressure in chambers 13 increases in a conventional manner, and refrigerant gas is pumped through the system containing the condenser 36, receiver 37, expansion valve 38 and cooling coil 39. After a period of operation the pressure in cooling coil 39 gradually reduces since the compressor capacity is usually selected to be greater than the loads encountered. This lowering pressure is transmitted to inlet opening 17 and is also sensed within the spool valve through the return passage 31. This lowered pressure is present throughout all of the chambers of the spool valve 22, such as top chamber 32 and the chambers surrounding connector means 25. As this suction, or lowered, pressure exceeds the forces provided by compression spring 28, the spool 24 will be drawn in a direction away from spring 28 toward top chamber 32. As the suction pressure from inlet opening 17 increases, that is, the pressure level falls, vents 19 and 21 will be progressively opened by the movement of spool enlargements 27 and 26, respectively, so as to provide a progressive bypass of the compressed refrigerant from chambers 13 back to inlet opening 17 through bleeder channel 31.

In the operation of one modification of this invention, the first bypass vent 19 in the downstream direction of the operation of the compressor is opened first. When it is nearly three-fourths open, for example, the enlarged portion 26 of spool valve 24 can be adjusted to begin opening bypass vent 21. After the opening of any bypass vent, the pressure in the outlet channel between outlet opening 18 and the rest of the system provides a back pressure which can produce erratic operation. To alleviate any problems created by such back pressure, a How valve 20 is provided in the outlet channel. This flow valve can be a fiap valve or the like, arranged so as to permit passage of refrigerant toward the condenser 36 but not back into the compressor.

The spacing of the bypass vents and the enlarged portions is determined by engineering considerations based on operational requirements for specific applications. One such application could require that the first bypass vent 19 could permit 20 percent of the refrigerant to be bypassed and permit percent of the refrigerant to continue through the refrigeration system through outlet 18. A maximum bypass could be percent, for example, by use of a vent such as vent 21 with the result that only 10 percent of the refrigerant would be available to the system. While only two bypass vents are shown, it is well within the teachings of this invention to provide as many bypass vents as desired for specific applications.

In the engineering of the bypass vents 19 and 21, the volume of the vents between the cylinder wall 16 and the valve enlargements 27 and 26 has been determined to be required to be less than one percent of the total compressor chamber volume. This, in an exemplary embodiment, is less than .02 cubic inch for a compressor of 2 cubic inches displacement. Since the volume is the critical quantity, and since the diameter of the vents should be as large as practicable for proper fluid flow therethrough, it is necessary to shorten the vents as much as is engineeringly feasible. Since the valve 22 is an adjunct to the compressor, the location of the valve in relation to the compressor permits short connections between the compressor and valve. The vents provide expansion and reexpansion problems to the operation of the compressor. The problems of resonance in the vents and crossbleeding between compressor chambers 13 are eliminated by maintaining a volume less than a maximum critical volume.

The plotted curve of B.t.u. capacity for the ordinates and pressure-temperature for the abscissas has a very smooth curvature of large radius for unmodulated compressor systems. A plot of the output of the modulated compressor of this invention would trace the plot of the unmodulated compressor as the suction pressure drops until the first vent is opened by the spool valve. At this time the curve would swing lower to follow a curve which is predictable by engineering considerations to result in lowering compressor capacity. This reduction in capacity through bypassing provides the necessary modulation, and at increased efficiency over that obtained with full compression bypass systems since compression to full discharge pressure is not required during modulation.

So it is seen that I have provided a new and improved compressor control system. Further, the modulated compressor of this invention progressively activates a valve to modulate the output of the compressor. The source of operating pressure for the control valve is on the input side of the compressor and, therefore, is fully responsive to demand. The overall power saving is substantial. The unnecessary work of compression is eliminated during moderate or low demand conditions because the recirculation of the refrigerant eliminates the power required to compress to high side pressures. This is accomplished with a constant speed compressor. Expensive bypass valves and control devices required in the prior art have been eliminated, and a comparatively inexpensive structure has been provided.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood, that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. In combination:

a refrigerant compressor unit having a wall defining a compression chamber with a low pressure side and a high pressure side,

an inlet opening at the low pressure side,

an outlet opening at the high pressure side and a plurality of venting means located at spaced intervals in said wall intermediate said inlet and outlet openings to progressively bypass a preselected quantity of said refrigerant; and

control means for controlling progressive compression relief during the compression stroke of said compressor unit,

said control means having a suction pressure responsive means, valving means, and mechanical connecting means connected to said suction pressure responsive means and said valving means;

fluid transmitting means connected between said low pressure side and said suction pressure responsive means, and a plurality of fluid transmitting means connected one between each of said plurality of venting means and one of each of a like plurality of said valving means;

said valving means operating in response to progressive increases in suction pressure to relieve successive venting means beginning with the venting means nearest the low pressure side and progressing toward the high pressure side.

2. In combination:

a refrigerant compressor unit having a low pressure side and a high pressure side, an inlet opening at the low pressure side, an outlet opening at the high pressure side and a plurality of venting means located intermediate said inlet and outlet openings to bypass progressively increasing quantities of said refrigerant; and

control means for providing progressive compression relief during the compression stroke of said compressor unit,

said control means having a suction pressure responsive bellows means, a selector means having a plurality of selector elements and means connecting said bellows means to said selector means to form a spool valve;

fluid transmitting means connected between said low pressure side and said bellows means, and

a plurality of fluid transmitting means connected one between each of said plurality of venting means and one of each of a like plurality of said selector elements;

said spool valve operating in response to progressive increases in suction pressure at the low pressure side to relieve successive venting means beginning with the venting means nearest the low pressure side and progressing toward the high pressure side.

3. In combination:

a refrigerant compressor unit having a low pressure side and a high pressure side,

an inlet opening at the low pressure side,

an outlet opening at the high pressure side and a plurality of venting means located intermediate said inlet and outlet openings to bypass progressively increasing quantities of said refrigerant; and

a spool valve located adjacent said compressor unit in the vicinity of said venting means,

said spool valve having a cylindrical chamber means,

a selector means slidably mounted within said chamber means, and a plurality of inlet aperture means,

a bleeder channel connecting said chamber means to said inlet opening,

a plurality of fluid conductor means connected one between one of each of said venting means and one of each of said inlet aperture means,

said selector means having refrigerant passage means therethrough to permit the remainder of said chamber to be filled with refrigerant,

said selector means having disc means which snugly fit within said chamber and located to selectively open said inlet aperture means to progressively increase the bypassed quantities of the refrigerant,

adjustable compression means mounted at one end of said cylindrical chamber,

connecting means connected between said selector means and said compression means,

said compression means balancing the inlet pressure in said chamber to properly locate said selector means; and

flow valve means connected to said outlet opening to prevent back pressure from entering the compressor unit.

4. The combination of claim 3 including wall means for containing said compressor unit and said spool valve.

5. The combination of claim 3 including wall means for containing said compressor unit and said spool valve in immediate vicinity of each other whereby the fluid conductor means between said venting means and said inlet aperture means are of minimum volume.

References Cited by the Examiner UNITED STATES PATENTS 219,114 9/1879 Ross 137-50518 1,858,517 5/1932 Marshall 62-196 2,328,824 9/1943 McCormack et a1. 230-138 2,462,039 2/1949 Gibson 230-31 2,730,269 1/1956 Earle et al 137-505.18

FOREIGN PATENTS 173,975 1/1961 Sweden.

MARK NEWMAN, Primary Examiner. DONLEY J. STOCKING, Examiner.

W. J. KRAUSS, Assistant Examiner. 

1. IN COMBINATION: A REFRIGERANT COMPRESSOR UNIT HAVING A WALL DEFINING A COMPRESSION CHAMBER WITH A LOW PRESSURE SIDE AND A HIGH PRESSURE SIDE, AN INLET OPENING AT THE LOW PRESSURE SIDE, AN OUTLET OPENING AT THE HIGH PRESSURE SIDE AND A PLURALITY OF VENTING MEANS LOCATED AT SPACED INTERVALS IN SAID WALL INTERMEDIATE SAID INLET AND OUTLET OPENINGS TO PROGRESSIVELY BYPASS A PRESELECTED QUANTITY OF SAID REFRIGERANT; AND CONTROL MEANS FOR CONTROLLING PROGRESSIVE COMPRESSION RELIEF DURING THE COMPRESSION STROKE OF SAID COMPRESSOR UNIT, SAID SECOND MEANS HAVING A SUCTION PRESSURE RESPONSIVE MEANS, VALVING MEANS, AND MECHANICAL CONNECTING MEANS CONNECTED TO SAID SUCTION PRESSURE RESPONSIVE MEANS AND SAID VALVING MEANS; FLUID TRANSMITTING MEANS CONNECTED BETWEEN SAID LOW PRESSURE SIDE AND SAID SUCTION PRESSURE RESPONSIVE MEANS, AND A PLURALITY OF FLUID TRANSMITTING MEANS CONNECTED ONE BETWEEN EACH OF SAID PLURALITY OF VENTING MEANS AND ONE OF EACH OF A LIKE PLURALITY OF SAID VALVING MEANS; SAID VALVING MEANS OPERATING IN RESPONSE TO PROGRESSIVE INCREASES IN SUCTION PRESSURE TO RELIEVE SUCCESSIVE VENTING MEANS BEGINNING WITH THE VENTING MEANS NEAREST THE LOW PRESSURE SIDE AND PROGRESSING TOWARD THE HIGH PRESSURE SIDE. 